In the past, loose powder cosmetic products were commonly applied to the skin through use of a puff. More recently, pressed powder products, such as face powder, eye shadow, blushes or the like have replaced the loose powder products and are produced by compressing loose powder into a metal pan using direct pressure. The pan containing the pressed powder cake is then glued into a compact or other container.
In the fabrication of pressed powder products, the pressure used in the pressing operation must be maintained within precise limits. If the pressure is too great, the metal pan may be distorted and must be discarded. In addition, utilizing a high pressure results in a cake which lacks the desired payoff characteristics. On the other hand, if the pressure is too low, the pressed cake will lack cohesive strength.
Further, certain powder compositions cannot be successfully used as a pressed powder cake because the pressure required to obtain the necessary cohesive strength will either distort the metal pan or produce a cake that is so hard that it lacks payoff.
To eliminate the problems associated with pressed powder products, non-pressed or poured powder cosmetic products have been proposed, as disclosed in U.S. Pat. Nos. 4,337,859 and 4,414,200. To form a non-pressed cosmetic product, a slurry is initially formed by mixing powdered materials, a binder such as a fatty acid, an evaporable carrier and pigments. The slurry is then poured into a container or mold, and on cooling and evaporation of the carrier, a solid product or cake is produced.
The powder cake, as produced by the aforementioned patents, can be formed directly in the compact or marketing container without the use of a metal pan as is required in pressed powder processes. By eliminating the use of the metal pan, the design configuration of the cake can be increased and the labor and assembly operations are greatly reduced.
It is has been noted that certain inorganic pigments, such as the oxides of iron, chromium and magnesium, possess a high degree of static charge. In a pressed powder product, the static charge does not present problems since the binders used in the pressed powder formulation tend to disperse the charges and the mechanical force of compression tends to hold the cake together.
However, in a non-pressed powder product, as disclosed in the aforementioned patents, the static charge on the pigments can cause color drift during filling and cracking of the cake on drying. These problems are further accentuated when small amounts of water from condensed steam used in the manufacturing process are present in the composition. It has been found that pigments tainted with water are attracted to various parts of the manufacturing equipment, such as the kettle, agitators and filling equipment, with the result that the slurry being poured into the mold or container does not contain all of the pigments of the formulation and shade drift or lack of color can occur when using multiple color pigments.